Research Interests

Epitaxial growth and strain in thin films

Introduction

Epitaxy means the oriented growth of a crystalline material on a crystalline substrate. As all magnetic properties of thin films depend on their surface/interface structure and their strain state it is indispensable to investigate the epitaxial growth of the thin films. There is a whole bunch of methods to investigate the epitaxial growth. We applied Auger Electron Spectroscopy (AES), Low Energy Electron Diffraction (LEED), Scanning Tunneling Microscopy (STM), and X-Ray Diffraction (XRD). With AES you can check the chemical cleanliness and the homogeneity of the films, whereas LEED is sensitive to the crystalline structure, strain, and chemical cleanliness (e.g. oxygen superstructure).

Influence of epitaxial strain on magnetic anisotropies

We studied thin Co films on W(110). The epitaxial strain was measured by high resolution LEED and the magnetic anisotropies were measured by TOM. Up to a thickness of 2 nm the films grow in a state of constant strain which results in a true volume-type anisotropy. Above 2 nm, a relaxation of strain is observed which scales roughly with 1/t and therefore results in an apparently surface-type contribution to strain anisotropy, superimposed on a reduced volume contribution.

Epitaxial Growth of bcc(110) films

It seems to be a common feature of bcc(110) films to have an anisotropic roughness with a lower roughness along the [001] direction than along the [1 -1 0] direction. So, the surface is composed of up and down staircases along [1 -1 0] and ridges along [001].